Heat Pump Not Heating? Winter Troubleshooting & Repair
Heat pumps deliver heat differently than gas furnaces — air from registers feels pleasantly warm (around 85°F to 95°F) rather than hot (120°F+ like a furnace). But if your heat pump is blowing cold air, running constantly without raising the temperature, or covered in thick ice, it needs attention. Here is how to tell normal winter operation from a component failure.
Normal heat pump behavior vs. actual trouble
Normal defrost cycle: during cold, damp weather, frost naturally forms on the outdoor coil. The unit will periodically shift into defrost mode for 5 to 10 minutes to melt the frost. Steam and humming from the outdoor unit during defrost are normal.
Actual icing failure: if the outdoor unit becomes encased in thick solid ice that doesn't melt, the defrost sensor, reversing valve, or defrost control board may have failed. Shut the system off to protect the compressor and call a technician.
Auxiliary / Emergency heat mode: in extreme cold below freezing, your heat pump's electric backup strips or secondary furnace should engage automatically to maintain temperature. If auxiliary heat never turns on, your thermostat or heat sequencer may be faulty.
What an on-site technician inspects
Refrigerant charge: low refrigerant prevents the heat pump from absorbing heat from outside air.
Reversing valve operation: the valve that switches the system from cooling to heating mode.
Defrost controls and outdoor fan motor: ensuring the outdoor unit can breathe freely in freezing weather.
Part of: Heat Pump Installation & Repair
A heat pump is an air conditioner that can run in reverse: it moves heat out of your house in summer and moves heat into it in winter. In moderate climates it can be the entire heating and cooling system; in cold climates it typically pairs with backup heat. The technology has improved dramatically — modern cold-climate heat pumps work well below freezing — but proper sizing, defrost setup, and realistic expectations about backup heat are what separate good installs from disappointing ones.
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Common questions
Heat pumps take a few minutes to bring the indoor coil up to operating temperature. If it continues blowing cold air for more than 10 minutes, the reversing valve or auxiliary heat may have an issue.
Only if the outdoor heat pump unit has completely failed or iced over. Emergency heat forces on the electric resistance strips, which keeps you warm but uses significantly more electricity until the primary unit is serviced.